TITLE:   GCN CIRCULAR
NUMBER:  16301
SUBJECT: GRB 140518A: Gemini-N redshift
DATE:    14/05/18 14:01:58 GMT
FROM:    Ryan Chornock at Harvard  <rchornock@cfa.harvard.edu>

R. Chornock (Harvard), D. B. Fox (Penn State), A. Cucchiara (Goddard), D. A. 
Perley (Caltech), and A. Levan (Warwick) report on behalf of a larger collaboration:

We obtained 2x900s of spectroscopy of the optical afterglow (Zheng et al., GCN 
16299; Perley et al., GCN 16300) of GRB140518A (Melandri et al., GCN 16298) 
using GMOS on the 8-m Gemini-North telescope starting at 12:22 UT on May 18. Our 
spectra covered the wavelength range 5900-10150 Angstroms at a resolution of 
R~1200. A damped Lyman-alpha system is present near 6940 Angs, corresponding to 
z~4.71.  A fit to the absorber gives z=4.706 and the log of the HI column 
density (in cm^-2) is 21.65 +- 0.1. Strong narrow absorption lines of S II, Si 
II, Si II*, O I, O I*, Si IV, C II, C IV, Fe II, and Al II associated with this 
absorption system have a common redshift of z=4.707.  The combination of the DLA 
and the excited fine structure lines allow us to identify this as the redshift 
of the GRB.

We thank the Gemini staff, in particular Rachel Mason and Joy Chavez, for their 
assistance with these observations.